I'm a bit lost on the contents of each frame and their durations and +ve or -ve voltages
It's usually unimportant, but it becomes important mainly because of combining software BFI and strobing. This duo amplifies inversion problems. Monitor manufacturers aren't expecting their display to be "assisted" with software black frame insertion, and combining hardware-strobing and software-BFI is simply a band-aid to successfully get what we want. (If we could get a single strobed monitor that supports 60Hz while having a 1/240sec QFT -- alas does not exist (and even ULMB+GSYNC 240Hz only provides 1/155sec QFT) -- so we gotta combine software BFI with hardware strobing to have cake and eat it too with low-lag 60Hz strobing.
For LCD inversion, most of the time we don't need to worry about it. Every even-numbered refresh cycles and odd-numbered refresh cycles alternate voltages. Technical explanations about LCD inversion electrical balancing is explained at at TestUFO
, at TechMind
, and at Lagom
. This is a normal feature in all LCD ever invented. Sometimes, occasionally, it creates an inversion artifact
This checkerboard texturing artifact (inversion artifact
) is amplified for 60fps@120Hz BFI on ULMB/LightBoost. But the problem almost completely disappears for software BFI 60fps@180Hz strobed, and you get full color depth back (no banding anymore) because it reduces interference with temporal dithering (6-bit FRC).
The checkerboard is positive-negative ... Imagine a chess board where black squares are negative voltages and white squares are positive voltages. And it alternates voltages the next refresh cycle. That's how LCD panels avoid a static charge buildup (image retention / burn-in effect). IPS panels don't have this artifact very visible, while TN panels have this more visible. As a rule of thumb, the faster the LCD (GtG becoming a tiny fraction of refresh cycle), the more likely the inversion artifact becomes visible.
If you black out one polarity, you end up getting a static charge buildup. That's what happens with software BFI. Monitors aren't expecting software BFI to be subjected to them. So 60fps@120Hz strobing (50% black:50% bright) and 60fps@240Hz strobing (75% black:25% bright) can cause the visible frame to be the same polarity, and lead to a burn in effect (image retention).
For end users,
the best software BFI (in terms of best color quality + least blur + lowest lag + avoiding burn in) on any currently available monitor, is the BenQ XL2546 running a custom 180Hz mode, and using a 2:1 software BFI ratio (66% dark, 33% bright, ala 2 black refresh cycles and 1 visible refresh cycle, for 60fps material).
For computer programmers,
there are workarounds to avoid burn-in issues (image retention) by occasionally inserting a duplicate BFI once every 15 seconds or so -- that's what I do at the TestUFO Flicker high speed camera test pattern. Also I helped the xash3d author do it in this thread
(see pages 1 and page 2), he added a clever anti-burn-in algorithm that I feel is a bit more complex than necessary but actually apparently works very well and automatically figures out which BFI Ratios causes burn in, and which BFI ratios don't cause burn in.
Also, not all LCDs will burn in with software BFI. I've run into some IPS LCDs that don't even burn in with software BFI, but their pixel response is much more laggy. The BFI burn-in (image-retention) happens more often with certain LCDs.
Now in addressing your desire of a 144Hz monitor, you can use 120Hz + large vertical totals + software BFI. For this I recommend the BenQ XL2430T or the XL2411P ... The color quality is very bad but they are very low lag, provides a 1/144 quick-frame-transport, and you can adjust strobe phase with Blur Busters Strobe Utility
. You can reduce strobe lag by adjusting strobe phase earlier but you will start to have strobe crosstalk (double image effects) caused by strobing a little too early. But you can still intentionally strobe early to reduce input lag if you want on certain BenQ monitors, as long as you don't mind double-image effects along the bottom edge of the screen.
Not all LCDs are realtime-scan, some of them buffer and scan out at their own merry velocity independent of the panel scanout. But as a rule of thumb, on most modern TN-based gaming LCD panels, they scanout synchronously at the highest Hz (e.g. 1/240sec at 240Hz, and 1/144sec at 144Hz). Some panels will truly multisync at custom resolutions (e.g. scan slower or faster) and some will only scanout at max velocity (e.g. buffer three-quarters of a framebuffer of a 60Hz input for 12ms before beginning to do a high-velocity scanout to panel -- this is a common problem with slow-scan signals on fast-scan-only panels -- but this is not applicable if you run in 240Hz mode anyway and intentionally treat it as a quick-frame-transport behavior as mentioned in earlier posts...). I've found certain BenQ monitors such as XL2735 behave this way; they aren't very Large Vertical Total friendly like XL2430T or XL2411P or XL2720Z or XL2420Z -- those models are truly multisync in terms of scanout velocity (cable scanout velocity equalling panel scanout velocity).
While mileage varies and there is overlap, I do get better color quality on several 240Hz monitors, and brighter strobing, than on several 144Hz monitors, so you should consider springing a premium. Many 240Hz monitors can strobe at 300 nits, so you still have roughly 100 nits left during 60fps@180Hz + software-BFI ...whereas with many other options you may be facing as little as 50 nits (quite dim). If bright strobing is important, the 25"-form-factor XL2546 (AMD+NVIDIA) and the 25"-form-factor 240Hz GSYNC monitors (NVIDIA) are the brightest-strobed monitors at the moment, if hardware-strobe brightness is a priority.